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The Physics of Crumbling a Wall
Posted: 29 November 2012 01:36 PM   [ Ignore ]
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Started playing with bullet physics, nearly crapped my pants. I made a scene but, I need help in re-working it so that it looks better. The scene is a docking bay where a large asteroid enters through the wall. I want the chunks to be of varying sizes and depths for more realism because when something crashes through, you won’t get uniform pieces flying everywhere. So I duplicated the asteroid over and over, then modified the shape of several pieces. I then stacked everything on the wall about to be crunched. Then I keyframed the asteroid to pass through the wall. Physics throws everything around nicely but, it’s that initial part where I’d like the wall to be smooth at first, then mangled as the rock rips through it.

I’m trying to ask a question without knowing the terminology—! Is there a way to pack the rock pieces inside a smooth shape that then breaks apart? Does that make any sense?

I’m also wondering if I should build interior layer of the wall with small flat uniform blocks (like little panels), then line the jagged pieces directly behind it so that when the asteroid passes through both layers it just scatters everything. Maybe that wouldn’t be too bad.

Any thoughts?

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Posted: 29 November 2012 02:45 PM   [ Ignore ]   [ # 1 ]
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“want the chunks to be of varying sizes and depths for more realism ‘

Just a thought - maybe the explode modifier will work along with physics. Explode ha s some control of size and speed over time.

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Posted: 29 November 2012 02:54 PM   [ Ignore ]   [ # 2 ]
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I have C7 Pro, so no bullet physics for me, but I know that others have used bullet and even Carrara’s non bullet physics engine to do stuff that’s similar to what you’re asking. Age of Armour even blew up a car using the old physics engine. Here’s a link to the video and another with a brief tutorial on how he did it:

http://www.youtube.com/watch?v=_eDov7NwxGU&feature=share&list=UULQ4IyzmRkwt07c1ikjvFwA

http://www.youtube.com/watch?v=-XGRj4VjPqk&feature=share&list=UULQ4IyzmRkwt07c1ikjvFwA

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Posted: 29 November 2012 02:55 PM   [ Ignore ]   [ # 3 ]
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I could certainly try that. I’m trying to add fire and smoke too, which I’m successful in varying degrees. The more I think about it, I think I’ll get better results if I put those chunks as a second wall layer that isn’t visible until the asteroid breaks through. The more detail I put into each piece, the better everything looks. That can probably be said of everything we do in Carrara.

Last night I had some trouble with the fire. I wanted it to shoot out and I keyframed it to follow the rock pieces as they flew horizontally into the room. But for some reason, the fire stayed back behind everything. Anyone know how to change that? I would suppose I’ll have the same issue with the smoke.

I will say this is A LOT of fun because you take these baby steps in your understanding of the software, then push yourself to learn new things. Very cool!

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Posted: 29 November 2012 03:26 PM   [ Ignore ]   [ # 4 ]
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The fire can be okay for some things, but it is really limited. It is not affected by physics or scene forces. You might be able to get better results using a particle generator.

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Posted: 29 November 2012 03:30 PM   [ Ignore ]   [ # 5 ]
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The explode modifier, and most other modifiers don’t work with Bullet physics.

In C8 , you can make good use of the replicator to take a chunk, or several chunks,. and create real instances with varying sizes.
(faster than adjusting a load of duplicates)
You can also take a Brick, and make a block wall.

You could also add that (bunch of chunks) into a Particle emitter,. although,.. particles don’t effect physical objects, they will collide with objects in the scene and add to the overall effect,.. if you also add some Scale variation to the (particle) Chunks being emitted.


For the Physics, if you’re using Bullet, the main issue with things like walls, will be the automatic collision detection for the blocks,. (pushing each other apart at the start of the simulation)

To avoid that,. Switch off the default scene gravity in the Physics tab, and replace it with a downward pointing “Direction Force”.
the force can be key-framed to change value over time,. so you can have a zero gravity (where no force pushes the blocks together)
then change it to a value similar to gravity when the collision happens.

If you’ve got your Asteroid key-framed,. then you’ll know what frame the physics kicks in on,. and you can set the (forces to kick in at that point.

You may also want to add some finer debris, or dust clouds,. and a Fog primitive,. emitted as a particle,. can be useful.
As can the fire primitive,..if you change the shape to sphere, and make the flames softer, you can get more of a gas / fireball effect.

You could also make a couple of objects and parent a Fire primitive to the object, then you have something that can be flying through the air,. on fire,..  and if you parent a particle emitter to that,. then you could have smoke particles trailing from it.

Just to add,.. you’re asteroid could also be using physics,. ..
What you need to do is set the “initial velocity” for the object,. you can set translation and rotation values for X,Y, Z, then simulate and the object will be propelled in the direction you’ve set ,... Like a ball being kicked or thrown.

Hope it helps wink

 

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Posted: 05 December 2012 10:11 AM   [ Ignore ]   [ # 6 ]
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3DAGE - how do I know if it’s bullet or just physics? What’s the difference?

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Posted: 05 December 2012 11:09 AM   [ Ignore ]   [ # 7 ]
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laynemoore - 29 November 2012 02:55 PM

The more I think about it, I think I’ll get better results if I put those chunks as a second wall layer that isn’t visible until the asteroid breaks through. The more detail I put into each piece, the better everything looks. That can probably be said of everything we do in Carrara.

I think this is the key. Hiding the complete wall on impact and unhiding the “debris” wall…

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Posted: 05 December 2012 11:28 AM   [ Ignore ]   [ # 8 ]
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HI smile

If you’re using C8, or the 8.5 beta,. there should be an option to use the old “Standard” carrara physics engine, or Bullet,
In the Scene Physics tab… pic

The “standard” physics engine, only supports Rigid body physics,.

Bullet is still being developed, but has support for Rigid body, Soft body, and constraints

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Posted: 05 December 2012 11:37 AM   [ Ignore ]   [ # 9 ]
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Ok, that helps. I’m using 8.5. The scene needs a lot of tweaking because my asteroid chunks tended to drift away from my room instead of collapse inside it. I’m seriously considering Phil Wilke’s training DVD. This trial and error method is a pain in the ass.

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